Add detailed comments for custom HttpClient setups

Clarify the purpose of HttpClient configurations in `SttpRestCallTest` and `JettyRestCallTest`. The added comments explain the use of a connection timeout significantly exceeding the CallTimeout value, improving code readability and maintainability.

Author: halotukozak

rest/.jvm/src/test/scala/io/udash/rest/SttpRestCallTest.scala

@@ -11,8 +11,11 @@ import scala.concurrent.duration.*
 import scala.concurrent.{Await, Future}
 
 trait SttpClientRestTest extends ServletBasedRestApiTest {
+  /**
+   * Similar to the defaultHttpClient, but with a connection timeout
+   * significantly exceeding the value of the CallTimeout
+   */
   implicit val backend: SttpBackend[Future, Any] = HttpClientFutureBackend.usingClient(
-    //like defaultHttpClient but with connection timeout >> CallTimeout
     HttpClient
       .newBuilder()
       .connectTimeout(JDuration.ofMillis(IdleTimout.toMillis))

rest/jetty/src/test/scala/io/udash/rest/jetty/JettyRestCallTest.scala

@@ -6,6 +6,10 @@ import io.udash.rest.{RestApiTestScenarios, ServletBasedRestApiTest}
 import org.eclipse.jetty.client.HttpClient
 
 final class JettyRestCallTest extends ServletBasedRestApiTest with RestApiTestScenarios {
+  /**
+   * Similar to the default HttpClient, but with a connection timeout
+   * significantly exceeding the value of the CallTimeout
+   */
   val client: HttpClient = new HttpClient() {
     setMaxConnectionsPerDestination(MaxConnections)
     setIdleTimeout(IdleTimout.toMillis)